- If you are one of the first ten patients enrolled in your cohort, you will take Dasatinib only on your first day of treatment (Day -1 of Cycle 1). On Day -1 and on Day 1 of Cycle 1, blood (about ½ teaspoon each time) will be drawn for pharmacokinetic (PK) testing before you take the drug and 1, 2, 4, and 8 hours after you take the drug. PK testing measures the amount of study drug in the body at different time points.